Low-profile and push-start lawnmowers and their engines

ABSTRACT

A family of rotary lawnmowers distinguished by one or more of the following characteristics: a structural integration of the shield and engine; coolant induction via the cutting blade; extremely low profile; absence of external flywheel; push-start capability; elimination of magneto ignition; and exhaust damping via discharge under shield.

United States Patent [72] lnvcntor John ,I. Horan 420 Quigley Ave,. Willow Grove, Pa. 19090 [21 1 Appl. No. 808,949 [221 Filed Mar. 20, 1969 [45] Patented July 27, 1971 [541 LOW-PROFILE AND PUSH-START LAWNMOWERS AND THEIR ENGINES 31 Claims, 13 Drawing Figs.

[52] U.S.Cl 56/102, 123/179, 56/175, 56/128 [51] Int. Cl ,.A0lld 35/26 [50] Field of Search 56/254, 255; 123/143, 148. 179, 185, 65 [561 References Cited UNITED STATES PATENTS 2,557,598 6/1951 Daggett 56/254 10/1955 Morris et a1. 56/25.4 2,791,078 5/1957 Kiekhaeferm. 56/25.4 3,063,436 11/1962 Wehner A. 123/179 3,063,437 11/1962 Wehner 123/179 3,076,448 2/1963 Wood, Jr. et all... 123/179 3,084,679 4/1963 Brown et a1 123/179 3,097,634 7/1963 Wehner 1. 123/179 3,119,382 l/l964 Gordon 123/179 3,134,375 5/1964 Schurra.... 123/179 3,521,434 7/1970 Emmerich 56/254 Primary Examiner-Russell R. Kinsey ABSTRACT: A family of rotary lawnmowers distinguished by one or more of the following characteristics: a structural integration of the shield and engine; coolant induction via the cutting blade; extremely low profile; absence of external flywheel; push-start capability; elimination of magneto ignition; and exhaust damping via discharge under shield.

PATENT E0 mm mm SHEET 2 [IF 6 PATENTEO JUL 21 m:

SHEET b 0F 6 PATENTEU JULE'HQ?! 3,594 996 sum 5 BF 6 PATENTEU JUL 2 7 I97] SHEET 6 BF 6 LOW-PROFILE AND PUSH-START LAWNMOWERS AND THEIR ENGINES RELATED APPLICATIONS Certain ignition features have appeared in my prior U.S. Pat. Nos. 3,430,080 and 3,349,760, as well as in applications Ser. Nos. 659,095, now Pat. No. 3,444,850, and 784,457. Other features have a relationship to U.S. Pat. Nos. 3,161,173 and 3,162,181.

BACKGROUND OF THE IN VENTlON In garden appliances powered by internal-combustion en gines, the appliance and its engine are customarily separately designed and built in different factories. One mower may carry any of several standardized engines and these engines in turn will be used with various series of mowers produced by different manufacturers and with other kinds of appliances. The improved economy and efficiency ofa fully integrated approach to the design problem has not heretofore been visualized.

Nearly all present day single-cylinder engines have ignition systems powered by magnetos. The necessity for accommodating these well-standardized systems has in turn forced a philosophy of design accommodation for these systems that has stifled forward thinking regarding engine design. The external flywheel is built to contain and be a part of the magneto; but, because it is impossible to seal this rapidly spinning large body that is also the coolant blower with reasonable reliability at low cost, the small ignition components are necessarily exposed to weather and other environmental hazards. Yet, access to these selfsame troublesome parts for diagnosis of failure is impossible with this same indispensable flywheel and its protective cover in place.

In turn again, the mass of the flywheel is necessarily displaced well outboard and far from its optimum position by reason of its eofunctions as an ignition housing and a coolant blower. Since it is thus far removed from the origin of the unbalance forces in the cylinder, its effectiveness for its primary job as a force balancer, energy storage medium, and damper of crank forces is gravely reduced, with the consequent imposition upon the perforcedly long, slender, and badly whipping crankshaft of large rocking couples and bending mo ments, causing excessive fatigue, wear, vibration, and noise. Termination of the traditional interdependence between the flywheel and the ignition system can be achieved with improvement to both; but this does not necessarily enforce the abandonment of the magneto per se. Yet, it provides an opportunity to take a fresh, uninhibited and unabashedly crea tive look at engine-powered appliances, including rotary lawnmowers, from both functional and cost standpoints, to determine whether the art can be advanced all along a broad front at once via the release of latent synergies. It is believed that this has been accomplished.

SUMMARY OF THE INVENTION The lawnmowers of this invention comprise a hedplate or main frame functioning as a structural bridge connecting the wheels, supporting the engine mechanism, and providing a shield over the spinning blade; and there the resemblance to mowers ofthe prior art terminates.

l have found that the bedplate or shield or main frame optionally may function also as a part of the enclosure and as a frame for the kinematic members of the power train, such as the reciprocating piston and/or the rotating crank mechanism. This contributes greatly to shortening the vertical shaft string, compacting the assembly, minimizing vibration and reducing the overall height.

1 have found a low-pressure area about the hub of the grasscutting blade noted that a great deal of air may be drawn down vertically thereinto via properly located openings in the shield thereabove. This air will then be accelerated in a spirally 'outward path above a blade that is pitched for cutting grass, particularly because of the serendipitous ability of the high-airdrag masses of clippings that are being transported in an expanding spiral to couple some of their kinetic energy into and thus help to entrain this air. Because the air entering the low pressure region no longer must move inwardly across the high velocity region, imposing severe flow disturbances and flattening the grass, there appears to be a smoothing of airflow at the blades, with diminution of power losses and of the former scattering ofcut particles in undesired directions.

With the removal of blower and ignition-system functions, the flywheel may be put inside the crankcase where its entire mass can contribute to stabilization of the force unbalances without generating large new rocking imbalances. As will be seen, it can now be made compactly of dense material and be so close to force origins as to check the unbalances almost directly and not via intervening hearings that are asymmetrically pounded or shafts that flex and fatigue and contribute to localized bearing wear.

The integration of engine functions into the shield or main frame, together with other novel features and constructions herein, eliminates an enormous number of parts seen in oldstyle mowers, cuts the overall weight drastically, and enables a striking reduction of bulk, which is conspicuously demonstrated by the small cubage and low overall height above the bedplate or main frame. This low profile enables the mower to be pushed under bushes, fences, etc., where there is minimum clearance; and it enables the consequent elimination of much supplemental trimming that formerly had to be performed by hand. I

Nor do the benefits stop there. Whereas the crankshafts of most mowers are very busy at both ends, because oftheir need to drive a multifunction, multibladed flywheel within a coolam-housing superstructure at the top, the lowprofile mowers herein have their shafts and other components so handily related as to render new functions at minimum cost.

One of these is a push-start capability. Easily engaged, simple, self-disconnecting mechanisms become possible and practicable because of the newly proximate: relationships between the transport wheels and the timing or other auxiliary shafts of the engine mechanism, which project therefrom only a short distance above the shield. When the mower is pushed, one or more of the wheels at one side wind up the engine continu ously instead of merely pushing the engine once past top center, as happens when it is manually cranked. They thus enable the fuel and airflow to optimize. Not only does starting become more certain and quicker, the back-breaking, heart attack-promoting labor associated with old forms of mowers is eliminated.

The relatively poor starting characteristics of small engines, especially those of the two-stroke-cyclc type, are alleviated by the rotary porting system shown and are completely overcome by the capability of the mechanical starting systems to rotate the engine continuously and without the usual pauses, compression reversals, etc. Though, for simplicity of disclosure drawings and descriptions, two-cycle drawings are shown, it will be obvious that provisions for a camshaft, valves, relocated carburetor, etc., in place of inlet, transfer, and exhaust ports can he made in accordance with widely known and commonplace practices in the art of building one-lung four strokers, and without interference with the illustrated relationships between reciprocating and rotating components and their housings.

The drawings and descriptions have been restricted in other ways to exclude details not directly relevant to the core of the inventive matter. For example, propulsion power takeoffs were not specifically described as such, though it is now obvious that my push-start apparatus can be redesigned for this purpose. Yet, one of the greatest benefits of the low mower heights achieved via these innovations is that riding mowers will no longer have to be made with wide treads and long wheelbases like those of garden tractors to stabilize them against overturning. The extremelv low height and rnmrmmness of the engine portion that projects above the shield enable the rider to sit far lower; in fact, his seat may be perched just above the shield with the engine between his knees. The resultant effect upon the overall center of gravity enables reduction of the footprint to dimensions more nearly commensurate with that of the cutting swath; and it slashes even more drastically the gross weight, horsepower requirement and cost of a low-profile riding mower of comparable performance.

BRIEF DESCRIPTION OF THE DRAWINGS Because the drawings are oriented primarily toward clarity of graphic presentation of inventive matter, the parts are not necessarily drawn to scale or in complete detail.

FIG. I is a cutaway partial plan view of a lawnmower in accordance with this invention.

FIG. 2 is a partial, sectional, left-side elevation of the lawnmower ofFlG. 1.

FIG. 3 is a partial, sectional, plan view within the crankcase of the lawnmower of FIG. 1.

FIG. 4 is a partial view from the underside of the lawnmower of FIG. 1.

FIG. 5 is a schematic diagram of an ignition system suitable for incorporation into the lawnmower of FIG. I.

FIG. 6 is a partial, sectional, left-side elevation of an alternative form oflawnmower in accordance with this invention.

FIG. 7 is a partial plan view of the lawnmower of FIG. 6 with the coolant shroud removed.

FIG. 8 is a partial plan view of the lawnmower of FIG. 6 showing the alternative push-start mechanism of the lawnmower.

FIG. 9 is a partial, partly cutaway, plan view showing details of an alternative form of push-start mechanism for the lawnmowers of this i..vention.

FIG. I0 is a partly cutaway fragmentary right elevation showing details of the push-start mechanism of FIG. 9.

FIG. 11 is a partly cutaway, partial plan view of an alterna tive form of push-start component mechanism for the lawnmowers of this invention.

FIG. 12 is a partly cutaway, partial elevation showing details of the push-start mechanism of FIG. 11.

FIG. 13 shows a plan view of an adaptation of the push-start mechanism of FIG. 6, applicable to the lawnmowers of this invention, arranged to be driven by the inboard hub of the right rear wheel.

DESCRIPTION OF THE EMBODIMENTS Referring now to FIGS. 1-5, the lawnmower has a bedplate or shield or main frame 30 adapted to be manually steered via handle 400. Plate or main frame 30 has an integral cylindrical member 31 which defines a cylindrical chamber for accommodating a horizontally reciprocating piston 32. Piston 32 is linked via connecting rod 33 to crankpin 34, which may optionally be integral with flywheel 35. However, for component longevity and low cost, crankpin may be made of hard, wearresistant bar steel and may be finished more smoothly and economically if it is designed to beproduced separately on the types of machines that make hex head capscrews. Such a screw may be passed through connecting-rod bearing 36 at as sembly, eliminating the usual requ rement for split bearings, connecting rod caps, and separate screws, which add to reciprocating weight and bulk and impair reliability and longevity in ordinary small engines. The diameter of the upper end of crankpin 34 has been reduced to a size convenient for driving timing shaft 37 via its integral valve plate 38. Valve plate 38 may thus be considered a crank, driven by crankpin 34.

Flywheel 35 is seen in FIG. 3 to have been partially relieved for compensation of the mass of the attached piston 32, its wristpin (not shown), and connecting rod 33, in order to balance inertia forces.

Taking full advantage of favorable manufacturing techniques, main shaft 39 has also been portrayed as it would look if optionally fabricated separately from flywheel 35 by screw-making techniques, Like crankpin 34, it has a reduced diameter portion 40 at one end, which portion 40 has been threaded to receive locknut 42, which fastens rotary blade 43 directly to shaft 39. Because they are close together on a short heavy shaft 39, blade 43 can be phased with the distributed mass of flywheel 35 for minimum vibration. One way to accomplish this is to key blade 43 via groove 40A to shaft por tion 40 so that it is perpendicular to the piston 32 when it is at top center (far left position). The broken lines in FIG. 2 show the blade position later. Keying the blade to the shaft, however, may cause damage if the blade encounters an obstruction. It may be wiser to forego the balancing advantage in most cases and permit the blade to slip between heavy washers or between the hex head and the retaining nut.

We may assume that pin 34 and shaft 39 can be of highly finished, hardened steel. Connecting rod 33 may be of material selected from a wide variety of pearlitic irons, steels, aluminum alloys, etc. Separate bearings 36 and 44 may be eliminated altogether by choosing connecting rod materials from among those which can serve as bearings, including some of the aluminum alloys. When the flywheel 35 is made with either of the pin or shaft integral, the choice among alloys is more limited; but when the pin or shaft are separate, the material becomes less critical. It must possess adequate mass and be able to withstand the centrifugal stresses to which it will be subjected at design r.p.m.

A cylinder liner 79 is shown. This may be of cast iron or steel. Alternatively, it may represent a hard surface coating on a shield cylinder casting or main frame of aluminum. If the casting is of a ferrous material, no liner would be used. Quite obviously a minimum of machining is required to prepare the casting to receive the mechanism.

If produced separately from the flywheel, pin 34 and shaft 39 may be staked in place as shown. Pin 34 is locked by a setscrew that is admitted via the transverse hole shown in dashed outline in FIG. 3. In this situation, centrifugal force would add to rather than lessen the locking force.

Sets of vertical cooling fins 46 and 47 are integral with shield casting or main frame 30, with the fins 47 being integral with the cylindrical member 31 as shown in FIGS. I and 2. The simple sheet metal or plastic shroud 48;, with air entry located at 49, and with one wall furnished by the inboard face of fuel tank 50, provides enclosure for upper coolant-circulation chamber SI, the shield 30 itself forming the twice-cooled wall between the upper coolant chamber 51 and the lower one below shield 30. The shield has a series of openings 55 between the chambers and just outside the periphery of crankcase cover 56. These openings permit passage of air from the upper chamber 51 downwardly into the portion of the lower chamber in which the pressure is least because of the centrifugal effect there of the rapidly spinning blade 43. Whether or not the blade 30 is cutting grass, the coolant passes outwardly in an expanding spiral pattern, washing the undersurface of shield 30 and its integral cylinder 31.

Instead of being impeded by the grass fragments that are being transported in a similar pattern toward chute 57, the airflow is now enhanced by the exchange of momentum therewith, owing to the excellent energy-coupling characteristics of the rough, high-drag, flying particles. Blade 43 could have additional cutting surfaces, paddles for increasing the airflow, etc.; however, a simple blade configuration with even less pitch angle than those commonly used today will generally be found superior.

The disturbing crossflows that scatter cut particles and waste energy in conventional mowers are seen to be eliminated. Also eliminated is the waste of energy by the conventional flywheel blower used in mowers of the prior art, with a further saving in bulk and weight. Circulation of the coolant air below the massive shield 30 provides a bonus cooling effect because it acts over the entire surface area of this large heat sink, there being also an evaporative thermal exchange with the alwayslavailable moisture in this zone. Even'the upper surface of this massive, large area heat sink that is integral with the cylinder walls contributes a radiative and convective removal of the heat that is conducted into it. The integrated shields mass and stiffness minimize engine vibration.

It will have been seen that, in addition to performing the normal functions of shields or bedplatcs' in rotary lawnmowers, shield 30 is also the principal component, framework, and housing for the engine assembly as well as the principal component, aside from blade 43, of the cooling system. A second cylinder might alternatively be cast into the shield so as to adapt any of a wide variety of plural'cylinder engine designs, well known in the art, to the functions taught here. Since such construction has been made obvious herein, no purpose would be served by adding showings to the specification and drawings.

The second major assembly is the timing assembly which includes crankcase cover 56 as its principal framework. This assembly might have been designed to include a 2:1 geared reduction for a cam or for valve cranks, together with valves, for operation as a four-strokecycle engine in accordance with well-known design principles for various families of such engines which usually have a larger number ofsmall parts.

Like the detailing of auxiliary propulsion gear, plural cylinder construction, etc., showings of four-strokccycle components, while fully compatible, would not have con tributed constructively to this disclosure. Therefore, for maximum simplicity, brevity, and clarity of presentation, these engincs have been completed as two-stroke-cycle embodiments.

Timing shaft 37, driven by crankpin 34 via its integral valve plate 38, rides in bearing 65 and is further separated from casting 56 by thrust bearing 66. As with bearings previously described, bearings 65 and 66 may be eliminated via choice of compatible materials for shaft 37, including plate 38 and nut 67 on one hand, versus casting 56 on the other. While the widely used reed valves might have been shown on the drawing, the opportunity to perform so many functions via a single high-quality steel shaft 37 inspired a decision to form it with an integral head 30 that will serve as a rotary valve plate, a slipper bearing on the crankpin, a thrust bearing on its upper surface, a carrier for spring-biased governor 60, and a timed closure for both the lower port 71 of transfer tube 59 and the inlet port 70 that communicates with the simple suction carburetor 60, which extends outwardly over fuel tank 50. With the shaft, it forms a crank. I

The bearing area of shaft 37 is recessed to include ignition cam 72 which communicates with ignition tube assembly 73, via a lateral opening in the bearing portion of casting 56. Pin 75, aligned to be engaged by the push-start assembly, is driven into a transverse hole in the upper end of shaft 37. This gives access for rotating the engine mechanism via shaft 37 and, if desired, even will enableshaft 37 to serve as a power takeoff for performing other work on the top side of the mower.

Thus, the functioning and accuracy of all regulating and timing means have been entrusted to a third small precision shaft, also adapted for economical close tolerance fabrication from a hard, long-wearing bar alloy. The multifunction compactness of shaft 37 contributes further toward manufacturing economy and the unprecedented compactness and low-profile it brings to outdoor appliances. As shown in phantom lines at 72A, the cam may, instead, be cut on shaft 39, casting 30 being relieved for access ofa follower, instead of casting 56.

The small governor plate 68 is pivoted about its broadheaded retaining screw 76, which carries it on the undersurface of valve plate 38. lts mass is so arranged that it swings outwardly against the restraint of cantilever spring 77 as the r.p.m. increases. As it swings, it tends to block inlet port 70, communicating with carburetor 60, which is mounted atop casting 56, and also block partially the transfer port '71, which leads to cylinder port 69 via transfer tube 59. Tube 59 is seen to be sealed at both ends with O-rings. As in many two-strokecycle engines, cylinder port 69 is cyclically uncovered by piston 32 soon after exhaust port 61 has been uncovered. Exhaust port 61 communicates with mufflcr64, a flattened tube closed at both ends and secured to the undersurface of shield 30 via a single fastener. The sets of small holes at its opposite ends are best unequally spaced from port 61. They eject the gas downwardly in fine jets which are broken up by the spiral flow existing there, the sound being further subdued by the occlusion of shield 30 and by the damping effect of the flying;

3,430,080 and in applications having Ser. Nos. 659,095 and" 784,457 and the battery-powered one shown schematically in FIG. 5 in which the dry cell itselfmay be contained within the tube and protected from the environment, eliminating all external wiring except a high-tension lead to spark plug80.

In FIG. 5, after switch 02 has been closed manually, cam 72 cyclically forces spring-rcstrained member 83 to open the gap between contact points 04 and 85, thus causing the magnetic field in primary coil 06 to collapse, resulting in the generation of a high voltage transient in secondary 87, which can be discharged to ground only via high-tension lead 31 and spark plug 80.

Shaft 37 might alternatively have been configured at its upper end to accommodate at its upper end any of such devices well known in the art as windlup starters and rope starters; but the mowers of this invention, because of their very low heights, are especially suited to carry any of the push starting means disclosed herein, which permit continuous cranking.

Slipper bearing 90, via which motion is imparted from crankpin 34 to shaft 37 during normal operation, compensates for possible lack of concentricity between shaft 39 and shaft 37, as located within their respective castings 30 and 56. It serves also to transmit force imparted to the opposite end of shaft 37 when starting the engine. The force is imparted via starting pin 75 by slotted starting collar 89, which is directly coupled to gear 91, which is seen in FIG. 1 to be meshed with pinion 92 in starting position.

Gear 91 and collar 09 are carried rotatably on stem 93, which is fixed in knob 94 by pin 95. This assembly is biased upwardly by springs 96 acting against clip 97. Clip 97 slidably straddles stanchions 98, which are bent over at their tops to limit the upward travel of this assembly. As the engine catches hold and begins to fire, thus accelerating shaft 37 in rotation and causing its transverse pin 75 to pull out of engagement with starting collar 89, springs 96 lift clip 97, together with collar 09, gear 91, and knob 94 as an assembly, separating gear 91 from bevel pinion 92, which remains held down by clip 100 that is secured to its shaft 103. Pinion 92 now moves transversely inwardly under the urging of spring 102 when thus released from gear 91.

The same laterally inward motion of shaft 103 serves also to release the inclined and slotted face of cup 104 from biting engagement against the inboard rims of rubber-tired wheels 105, 106 on the right side of the mower. Each of these wheels is carried on its own adjustment arm 107, 100 respectively, the arms being rotatable downwardly or upwardly about the center of shaft 103, for adjustment of the height of shield 30 and blade 43 above the ground. The arms may be clamped at any desired setting by tightening bolts 109, 110, 111, and 112. To compensate for any effect of whee1 height adjustment upon the shaft position at which cup 104 best contacts wheels 105, 106, turnbuckle 113 may be rotated.

F168. 6, 7, and 0 illustrate an alternative version of the lowprofile lawnmower in which crankcase housing 156, rather than engine cylinder 131, is integral with shield 130. Reciprocating components and those located within crank- The flywheel mass 135 is again located inside the crankcase 156; and all of the piston 32 and blade 43 reaction may again be taken by the single set of bearings 44, 45, 45 clustered at the bottom wall opening of crankcase 156. Of course, these bearings might alternatively be replaced by ball, roller or com bination types, especiallyif it is desired to spin the blade at higher speeds. Connecting rod 133 terminates in a male pintle 134, which rotates in a bearing opening in flywheel 135. It carries a spur pin 190, which may be forged integrally with connecting rod 133 or may be rotatably mounted therein. Only in the latter case can it be given flattened sides for long life in a slipper bearing if such is used above. As before, it drives upper shaft 37. It will be noted that this construction enables lowering the height of the engine slightly more than in the prior case.

The detachable cylinder 131 is secured by capscrews 114 and bolts 111 to the open face of crankcase housing 156. Also detachable is the crankcase cover 122, into which the timing shaft 37, like that described previously, is assembled. The showing of carburetor 60 has been omitted here to reduce the amount of detail. Since the seat in the crankcase housing for cover 122 and the bore for receiving shaft 39 are likely to be finish machined by tooling mounted upon a common center, there may be additionaljustification for providing a 360 bearing in valve plate 38. Because cover 122 needs its peripheral sealing means to be higher at its forward end, a second groove has been cut here to carry the forward portion of the O-ring, Shield 130 also has vertical coolant openings 155 arranged around crankcase wall 156 to feed the central low-pressure zone below with air passing from port 149 via space 151 adright, being angled downwardly. Bracket 115 has an elongated vertical slot to permit both upward and longitudinal movement of shaft 116, upon which pinion 192 is fixed. Shaft 116 is adjustable in length where the small-diameter end enters the larger portion 127 and may be locked in length adjustment by jamnut 117. Bracket 120, secured to shield 130, has a cylindrical bore for receiving spring-biased 121 plunger 122, indicated by dashed lines. As bias block 123, within which shaft 127 is fixed longitudinally but free to rotate, slides to the right within the slanted slot in plunger 122, it is forced forwardly by stiff spring 121. This causes slotted wheel 124 to engage the rubber tread of forward right-hand wheel 125 for push-start actuation of the engine. When the engine starts to run, the pinion gear assembly 119, 191, 192 is thrust upwardly out of engagement with shaft 37, whereupon it moves to the left under the urging of spring 118, releasing the compression of spring 121 and the bite of driven wheel 124 against wheel 125, the normal position of the corner of bracket 119 being indicated by broken lines.

Closed-endedmuffler 164 is held down upon bedplate 130 by screws 126, which keep it located with its upwardly turned mouth thrusting into port 161. Again, it will be seen that the hole arrays on opposite sides are at unequal distances from port 161. However, the quality of sound damping here is inferior to that in the prior case when sound was muffled under the shield and damped by cuttings.

In FIGS. 9 and 10, the push starter is related generally but not in detail to those preceding it. Shaft 200 is secured firmly to pinion 202, which is meshed with gear 201, cut into flywheel 235 and contained within crankcase 256 upon shield 230. Coolant cover 248 and crankcase 256 are cut away to show details. Projections 204 and 205 arise from bedplate 230 and are attached thereto by any convenient means including integral casting. Projection 204 latches the notch of shaft 200 against the laterally outward pressure of spring 206, which is poised to disengage pinion 202 from gear 201 and allow it to move toward the right side of the mower. Unlike the angled prior shaft, shaft 200 is horizontal and lies close to shield 230.

To seal the side of crankcase 256, a slidable plate 207 has an O-ring-sealed face and a second O-ring for the shaft opening. Removable wheel 208 is of big enough-diameter to displace the two right side wheels off the ground; so it carries the full weight of the right side while the left side remains on its wheels. When the engine starts, bevel gear 201 accelerates with the clockwise rotation of'the flywheel 235, forcing pinion 202 to move aft and disengaging shaft 200 from latch 204. Projection 205 has a transverse clearance cut therethrough just wide enough and so aligned with the opening in crankcase 256 to accommodate the latehing/unlatching excursions of shaft 200. When the engine has started, wheel 208 may be removed by grasping handle 209 and placed in its stowed position on finger 210 atop coolant cover 248.

As we refer now to FIGS. 11 and 12, we recall that, in the comparable FIGS. 1 and 2, cylinder 31 defined by the casting 30 that formed a bottom frame for carrying the flywheel and blade. This is again true of housing 331; however, shield 330 is a separate plate of sheet metal fastened to housing 331 by screws 301 302, 303 and 304. Crankcase-cover casting 356 is generally similar to cover 56 of the earlier embodiment; and other components, such as carburetor 60'and transfer tube 359 are also similar. However, the cover casting 356 has an opening in the side and supports magneto Ecoil 305 sealably over the opening so that the E-coil may feel the rapidly changing level of flux as a pair of magnets carried on the flywheel sweeps past it inside the crankcase once per engine revolution. This resembles the magneto arrangement seen in my earlier U.S. Pats. Nos. 3,161,173 and 3,l62,18l. The breaker points may be carried in a tubular housing resembling 73 of FIG, 1 and actuated by cam 372, which resembles cam 72 of the earlier showing herein. Such an ignition system may be substituted for any of the systems shown in prior figures, because these engines are fully compatible with representative ignition circuitry of the prior art.

As may best be seen in FIG. 11, wherein coolant cover 348 v has been cut away, coolant openings 307 and 308, interposed between shield 330 and engine housing 331, together with hidden symmetrical openings on the left side, provide ample opening area for transit of coolant air from upper compartment 351 to the low-pressure zone below.

Another difference noted in this embodiment is in its pushstart mechanism. Here a flexible shaft drive 313 is contained within nonrotating sleeve 314. Shaft 313 is driven by the inner end 312 of live axle 311, to which the sleeve adapter 310', the sleeve 314, and thumbwheel 317 offer continuous covering. The assembly rises through a hole in shield 330 outside the swept circle of blade 43, a small closure plate 323 being provided to facilitate installation and removal of the large-diameter terminal adapter 310. The shaft terminates at its inboard end in rigid stub 315, which has a transverse pin 316 therethrough, as seen via the cutaway portion of the knurled thumbwheel 317. The thumbwheel 317 provides a convenient grip for aiding the manual coupling of shaft stub 315,316 with the forked upper end of engine shaft 337, which projects above nut 319 and out through a hole in coolant cover 348. A spring 320 biases thumbwheel 317 upwardly against the restraint of bracket 321. To engage stub 315 with forked shaft terminus 318, thumbwheel 317 is rotated clockwise while held down. If desired, the mower may be pushed slightly to aid in indexing stub 315 into terminus 318.

When the mower is then pushed with its ignition on, the engine is continuously revolved until it starts and acquires sufiicient rpm. to overrun and separate from stub 315.

Suction carburetor 60 is seen best in these figures to project aft from its position atop casting 356 from the aft end of C00- lant chamber cover 348. The fact that it lies across part of fuel tank 324 permits easy alignment of a fuel intake tube on its underside (not seen) with a hole in the top of the tank. Tank 324, except for its lesser height, resembles the low-cost commercial gallon cans used for shipping a wide variety of fluids such as varnishes and cements. The carburetor 60 terminates in a broad flange that serves as a base for a coil spring that stretches out the knit-sock type of air filter 325.

Referring now to FIG. 13, there is seen an arrangement alternative to that seen in FIG. 8 for the outboard end of that push-start assembly. This one is somewhat simpler and may or may not need to be angled downwardly in the manner of the shaft assembly of FIG. 8. As may be seen, it is angled aft for engagement with the right rear wheel 380. Wheel 380 has an enlarged tapered inboard hub 38], which is engaged by the tapered elastomeric surface of driven wheel 382 for push-start actuation of an inboard engine.

Bracket 383, in which the fixed shaft 384 of wheel 382 is free to slide and rotate, is fixed to shield 385. Spring 387, bearing against collar 388 which is welded onto shaft 384, urges the shaft 384 inwardly for disengagement upon release of its inboard end (not seen) from the engine after the latter has started. Driven wheel 382 has been presented as having its axis on the same level as the center of wheel 380. Obviously, however, engagement is also possible between appropriately configured surfaces when the axis of wheel 382 is well above the centerline of wheel 380. It is not essential that the rotating shaft of the push-start mechanism be flexible. it may be rigid, for example, with joints articulated by universals which, in some cases, might need a measure of outside support near the joint so they will not buckle out ofengagement.

Obviously, mowers, engines, and components of the character introduced herein may take on other configurations differing in detail from the representative types shown herein without departing from the scope of these teachings. The number of specific showings herein is a bare minimum, restricted to avoid prolixity; and many more could have been presented were it not for the objective of speedy prosecution.

It is intended that objects deducible from the disclosures by one skilled in the art be covered by the claims. Therefore, I claim:

1. A combustion-powered rotary lawnmower comprising:

a main frame;

a complement of surface-transport wheels,

said main frame being supported on said wheels;

crankcase means associated with said main frame,

said crankcase means having a vertical opening through a lower wall thereof;

a crank having a shaft depending therefrom,

said shaft bearing rotationally in said opening and depend ing into said frame;

cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular-cutting swath thereabout,

said wheels being located beyond the periphery of said swath;

combustion chamber means associated with said crankcase means; and

a reciprocating piston assembly disposed within said cmbustion chamber means and mechanically coupled to said crank for rotation thereof,

said lower wall constituting a portion of said main frame and defining therewith the cutting chamber in which said cutting blade means operates,

at least one of said lower wall and said combustion chamber means being integral with said main frame.

2. A lawnmower as in claim it,

said one being the lower wall.

3. A lawnmower as in claim 1,

said one being the combustion chamber means.

4. A lawnmower as in claim 1,

said cutting blade means being configured to generate,

when operatively rotated by said shaft under combustion power, a generally central low-pressure zone and an airflow directed outwardly between said cutting blade means and said main frame from said zone.

5. A lawnmower as in claim 4,

said main frame having therein an opening for removing coolant air passing close to said combustion chamber means,

said opening being located for induction of said passing air by said cutting blade means downwardly into said zone.

6. A lawnmower as in claim 1,

said shaft having a normal direction of rotation,

said lawnmower comprising also:

handle means secured to said main frame for pushing said main frame in a desired direction on said wheels; and

a push-start apparatus supported on said main frame,

said apparatus being adapted to transfer, from at least one of said wheels when rolling in said desired direction, a torsional moment for rotating said shaft in said normal direction when said combustion chamber means is not in operation,

said apparatus including a manually engageable coupling mechanism,

said mechanism being disengageably sensitive to reversal of the sign of the torsional moment that exists therein when said apparatus is producing rotation in said shaft.

7. A combustion-powered rotary lawnmower comprising:

a main frame;

a complement of surface-transport wheels,

said main frame being supported on said wheels;

crankcase means associated with said main frame,

said crankcase means having a vertical opening through a lower wall thereof;

a crank having a shaft depending therefrom,

said shaft bearing rotationally in said opening and depending into said frame;

cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular cutting swath thereahout,

said wheels being located beyond the periphery of said swath;

combustion chamber means associated with said crankcase means; and

a reciprocating piston assembly disposed within said combustion chamber means and mechanically coupled to said crank for rotation thereof,

said combustion chamber means being integral with said main frame.

8. A lawnmower as in claim 7,

said piston assembly including a connecting rod extending into said crankcase means,

said crankcase means including an upper wall above said connecting rod,

the lower face of said upper wall being below the maximum height ofthe piston of said assembly.

9. A lawnmower as in claim 7,

said lower wall being integral with said main frame.

lit). A lawnmower as in claim 7,

said cutting blade means being configured to generate, when operatively rotated by said shaft under combustion power, a generally central low-pressure zone and an airflow directed outwardly between said cutting blade means and said main frame from said zone.

11. A lawnmower as in claim 10,

said main frame having therein an opening for removing coolant air passing adjacently to said combustion chamber means,

said opening being located for induction of said passing air by said cutting blade means into said. zone.

12. A lawnmower as in claim 7 and comprising also:

handle means for pushing said main frame in a desired direction on said wheels; and

a pushstart apparatus supported on said main frame,

said apparatus being adapted for optional rotational connection between at least one of said wheels and said shaft when said combustion chamber means is not in operation,

said shaft having a normal direction of rotation,

said apparatus including a manually engageablc unidirectional coupling mechanism responsive to the torsional moment imposed thereon when said one wheel is rolled in the desired direction,

said mechanism being aligned to rotate said shaft in said normal direction and to be drivably disengaged therefrom when said shaft accelerates to a higher speed.

13. A combustion-powered rotary lawnmower comprising:

a main frame;

a complement of surface-transport wheels,

said main frame being supported on said wheels;

cran. case means associated with said main frame,

said crankcase means having a vertical opening through a lower wall thereof;

a crank having a shaft depending therefrom,

said shaft bearing rotationally in said opening and depending into said frame;

cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular cutting swath thereabout,

said wheels being located beyond the periphery of said swath;

combustion chamber means associated with said crankcase means; and

a reciprocating piston assembly disposed within said combustion chamber means and mechanically coupled to said crank for rotation thereof,

said cutting blade means being configured to generate, when operatively rotated by said shaft under combustion power, a generally central low pressure zone and an airflow directed outwardly from said zone through the space between said cutting olade means and said main frame,

said main frame having therein an opening for removing cooling air passing adjacently to said combustion chamber means,

said opening being located for induction of said passing air into said zone.

M. A lawnmower as in claim 113,

having wall means defining a boundary for coolant air passing said combustion chamber means.

15. A lawnmower as in claim 14,

wherein part of said wall means is below said combustion chamber means.

16. A lawnmower as in claim 13,

wherein the undersurface of said combustion chamber means forms part of the upper boundary for said air when directed through said space.

17. A lawnmower as in claim to,

the said combustion chamber means having an exhaust opening on the undersurface thereof.

18. A lawnmower as in claim 33,

said lower wall being integral with said frame.

19. A lawnmower as in claim 13,

said combustion chamber means being integral with said main frame.

20. A lawnmower as in claim 13,

said shaft having a normal direction of rotation,

said lawnmower comprising also:

handle means for pushing said lawnmower in a desired direction on said wheels; and

a push-start apparatus adapted for connection of at least one of said wheels rotatably to said shaft when said com bustion chamber means is not in operation,

said apparatus including a coupling mechanism for completing said connection,

said mechanism being adapted for continuous transmission from said wheel to said shaft of torque in said normal direction when said wheel is rolled in said desired direction,

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said connection being discontinuous when combustion power accelerates said shaft to a higher speed in said normal direction.

21. An engine-powered lawnmower comprising:

a main frame having an opening therein for admitting a vertical shaft;

a complement of surfacetransport wheels,

said main frame being supported on said wheels;

means for manually pushing said frame on said wheels in a desired direction;

engine means associated with said main frame and having a vertical output shaft depending therefrom into said frame via said opening,

said shaft having a normal direction of rotation;

cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby in said normal direction, a circular cutting swath thereabout,

said wheels being located beyond the periphery of said swath; and

a self-starting apparatus, supported on said frame and adapted for optional rotational connection between at least one of said wheels and said shaft,

said apparatus including a coupling mechanism for completing said connection,

said connection being continuously operative in said normal direction when said lawnmower is being pushed in said desired direction,

said mechanism being disengageably responsive to acceleration of said shaft to a higher velocity by said engine means in said normal direction than the velocity being imparted to said shaft by said wheel via said apparatus,

whereby said apparatus will automatically disengage itself from operative connection to said shaft after said engine means has been started thereby.

22. A lawnmower as in claim 21,

said coupling mechanism including spring means positioned for retaining said mechanism in such completed connection and poised for forcible disengagement of said mechanism upon such acceleration.

23. A lawnmower as in claim 21,

said apparatus being adapted for rotational contact against the periphery of said one wheel when said connection is complete.

24. A lawnmower as in claim 21,

said apparatus being axiallyjoined to said one wheel.

25. A lawnmower as in claim 21,

said apparatus including toothed rotational drive means.

26. A lawnmower as in claim 21,

said apparatus including flexibleshaft interconnection means.

27. A lawnmower as in claim 21,

said apparatus including means for transforming the torsional moment between said at least one wheel and said shaft.

28. A lawnmower as in claim 21,

said apparatus including an angular drive means.

29. A combustion-powered rotary lawnmower comprising:

a main frame;

a complement of surface-transport wheels,

said main frame being supported on said wheels;

crankcase means associated with said main frame,

said crankcase means having a vertical opening through a lower wall thereof;

a crank having a shaft depending therefrom,

said shaft bearing rotationally in said opening and depend ing into said frame;

cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular cutting swath thereabout,

said wheels being located beyond the periphery of said swath;

combustion chamber means associated with said crankcase means; and

tive cooling thereof by said airflow.

30. A lawnmower as in claim 29,

said combustion chamber means being situated for cooling by said discharge portion.

31. A lawnmower as in claim 29,

said combustion chamber means being situated for cooling by said upstream portion. 

1. A combustion-powered rotary lawnmower comprising: a main frame; a complement of surface-transport wheels, said main frame being supported on said wheels; crankcase means associated with said main frame, said crankcase means having a vertical opening through a lower wall thereof; a crank having a shaft depending therefrom, said shaft bearing rotationally in said opening and depending into said frame; cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular-cutting swath thereabout, said wheels being located beyond the periphery of said swath; combustion chamber means associated with said crankcase means; and a reciprocating piston assembly disposed within said combustion chamber means and mechanically coupled to said crank for rotation thereof, said lower wall constituting a portion of said main frame and defining therewith the cutting chamber in which said cutting blade means operates, at least one of said lower wall and said combustion chamber means being integral with said main frame.
 2. A lawnmower as in claim 1, said one being the lower wall.
 3. A lawnmower as in claim 1, said one being the combustion chamber means.
 4. A lawnmower as in claim 1, said cutting blade means being configured to generate, when operatively rotated by said shaft under combustion power, a generally central low-pressure zone and an airflow directed outwardly between said cutting blade means and said main frame from said zone.
 5. A lawnmower as in claim 4, said main frame having therein an opening for removing coolant air passing close to said combustion chamber means, said opening being located for induction of said passing air by said cutting blade means downwardly into said zone.
 6. A lawnmower as in claim 1, said shaft having a normal direction of rotation, said lawnmower comprising also: handle means secured to said main frame for pushing said main frame in a desired direction on said wheels; and a push-start apparatus supported on said main frame, said apparatus being adapted to transfer, from at least one of said wheels when rolling in said desired direction, a torsional moment for rotating said shaft in said normal direction when said combustion chamber means is not in operation, said apparatus including a manually engageable coupling mechanism, said mechanism being disengageably sensitive to reversal of the sign of the torsional moment that exists therein when said apparatus is producing rotation in said shaft.
 7. A combustion-powered rotary lawnmower comprising: a main frame; a complement of surface-transport wheels, said main frame being supported on said wheels; crankcase means associated with said main frame, said crankcase means having a vertical opening through a lower wall thereof; a crank having a shaft depending therefrom, said shaft bearing rotationally in said opening and depending into said frame; cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular cutting swath thereabout, said wheels being located beyond the periphery of said swath; combustion chamber means assocIated with said crankcase means; and a reciprocating piston assembly disposed within said combustion chamber means and mechanically coupled to said crank for rotation thereof, said combustion chamber means being integral with said main frame.
 8. A lawnmower as in claim 7, said piston assembly including a connecting rod extending into said crankcase means, said crankcase means including an upper wall above said connecting rod, the lower face of said upper wall being below the maximum height of the piston of said assembly.
 9. A lawnmower as in claim 7, said lower wall being integral with said main frame.
 10. A lawnmower as in claim 7, said cutting blade means being configured to generate, when operatively rotated by said shaft under combustion power, a generally central low-pressure zone and an airflow directed outwardly between said cutting blade means and said main frame from said zone.
 11. A lawnmower as in claim 10, said main frame having therein an opening for removing coolant air passing adjacently to said combustion chamber means, said opening being located for induction of said passing air by said cutting blade means into said zone.
 12. A lawnmower as in claim 7 and comprising also: handle means for pushing said main frame in a desired direction on said wheels; and a push-start apparatus supported on said main frame, said apparatus being adapted for optional rotational connection between at least one of said wheels and said shaft when said combustion chamber means is not in operation, said shaft having a normal direction of rotation, said apparatus including a manually engageable unidirectional coupling mechanism responsive to the torsional moment imposed thereon when said one wheel is rolled in the desired direction, said mechanism being aligned to rotate said shaft in said normal direction and to be drivably disengaged therefrom when said shaft accelerates to a higher speed.
 13. A combustion-powered rotary lawnmower comprising: a main frame; a complement of surface-transport wheels, said main frame being supported on said wheels; crankcase means associated with said main frame, said crankcase means having a vertical opening through a lower wall thereof; a crank having a shaft depending therefrom, said shaft bearing rotationally in said opening and depending into said frame; cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular cutting swath thereabout, said wheels being located beyond the periphery of said swath; combustion chamber means associated with said crankcase means; and a reciprocating piston assembly disposed within said combustion chamber means and mechanically coupled to said crank for rotation thereof, said cutting blade means being configured to generate, when operatively rotated by said shaft under combustion power, a generally central low-pressure zone and an airflow directed outwardly from said zone through the space between said cutting blade means and said main frame, said main frame having therein an opening for removing cooling air passing adjacently to said combustion chamber means, said opening being located for induction of said passing air into said zone.
 14. A lawnmower as in claim 13, having wall means defining a boundary for coolant air passing said combustion chamber means.
 15. A lawnmower as in claim 14, wherein part of said wall means is below said combustion chamber means.
 16. A lawnmower as in claim 13, wherein the undersurface of said combustion chamber means forms part of the upper boundary for said air when directed through said space.
 17. A lawnmower as in claim 16, the said combustion chamber means having an exhaust opening on the undersurface thereof.
 18. A lawnmower as in claim 13, said lower wall being integral with said frame.
 19. A lawnmower as in claim 13, said combustIon chamber means being integral with said main frame.
 20. A lawnmower as in claim 13, said shaft having a normal direction of rotation, said lawnmower comprising also: handle means for pushing said lawnmower in a desired direction on said wheels; and a push-start apparatus adapted for connection of at least one of said wheels rotatably to said shaft when said combustion chamber means is not in operation, said apparatus including a coupling mechanism for completing said connection, said mechanism being adapted for continuous transmission from said wheel to said shaft of torque in said normal direction when said wheel is rolled in said desired direction, said connection being discontinuous when combustion power accelerates said shaft to a higher speed in said normal direction.
 21. An engine-powered lawnmower comprising: a main frame having an opening therein for admitting a vertical shaft; a complement of surface-transport wheels, said main frame being supported on said wheels; means for manually pushing said frame on said wheels in a desired direction; engine means associated with said main frame and having a vertical output shaft depending therefrom into said frame via said opening, said shaft having a normal direction of rotation; cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby in said normal direction, a circular cutting swath thereabout, said wheels being located beyond the periphery of said swath; and a self-starting apparatus, supported on said frame and adapted for optional rotational connection between at least one of said wheels and said shaft, said apparatus including a coupling mechanism for completing said connection, said connection being continuously operative in said normal direction when said lawnmower is being pushed in said desired direction, said mechanism being disengageably responsive to acceleration of said shaft to a higher velocity by said engine means in said normal direction than the velocity being imparted to said shaft by said wheel via said apparatus, whereby said apparatus will automatically disengage itself from operative connection to said shaft after said engine means has been started thereby.
 22. A lawnmower as in claim 21, said coupling mechanism including spring means positioned for retaining said mechanism in such completed connection and poised for forcible disengagement of said mechanism upon such acceleration.
 23. A lawnmower as in claim 21, said apparatus being adapted for rotational contact against the periphery of said one wheel when said connection is complete.
 24. A lawnmower as in claim 21, said apparatus being axially joined to said one wheel.
 25. A lawnmower as in claim 21, said apparatus including toothed rotational drive means.
 26. A lawnmower as in claim 21, said apparatus including flexible-shaft interconnection means.
 27. A lawnmower as in claim 21, said apparatus including means for transforming the torsional moment between said at least one wheel and said shaft.
 28. A lawnmower as in claim 21, said apparatus including an angular drive means.
 29. A combustion-powered rotary lawnmower comprising: a main frame; a complement of surface-transport wheels, said main frame being supported on said wheels; crankcase means associated with said main frame, said crankcase means having a vertical opening through a lower wall thereof; a crank having a shaft depending therefrom, said shaft bearing rotationally in said opening and depending into said frame; cutting blade means fixed at the lower end of said shaft to generate, when rotated thereby, a circular cutting swath thereabout, said wheels being located beyond the periphery of said swath; combustion chamber means associated with said crankcase means; and a reciprocating piston assembly disposed within said combustion chambeR means and mechanically coupled to said crank for rotation thereof, said cutting blade means being configured to generate an airflow when so rotated, said airflow having upstream and discharge portions, said discharge portion flowing outwardly above said blade means and below said frame, said combustion chamber means being situated for convective cooling thereof by said airflow.
 30. A lawnmower as in claim 29, said combustion chamber means being situated for cooling by said discharge portion.
 31. A lawnmower as in claim 29, said combustion chamber means being situated for cooling by said upstream portion. 